1. Field of the Invention
The present invention relates generally to the field of x-ray imaging systems. More specifically, it relates to an anti-collision method and apparatus for use with a C-arm x-ray imaging machine for preventing serious collisions between patients, operators and the equipment itself.
2. Background of the Invention
It is frequently desired to conduct an x-ray examination of a patient from several different positions and is often preferable to do so without the need to reposition the patient. Mobile C-arm X-ray diagnostic machines, such as that shown in FIG. 1, have been developed to meet these needs and are now well known in the medical and surgical arts. The C-arm x-ray machine is especially useful in that it is small enough and mobile enough to be present in an operating or exam situation without requiring the physician to repeatedly move or requiring the patient to change positions to obtain a suitable image.
The term xe2x80x9cC-armxe2x80x9d refers to the C-shaped member of the machine that contains an x-ray source and an image receptor mounted on opposing ends of the C-arm such that x-rays emitted by the source are incident on and detected by the image receptor. The source and the image receptor are positioned such that when, for example, a human extremity is interposed between the x-ray source and the image receptor and irradiated with x-rays, the receptor produces data representative of characteristics of the interposed object. The data produced is typically displayed on a monitor and electronically stored.
The C-arm itself is normally mounted such that it is permitted two degrees of freedom. First, the C-arm track is slidably mounted to the support member so as to be movable in relation to the support member. This permits the x-ray source and image receptor to be moved rotatably about the arc of curvature of the track in the C-arm. The C-arm support member also permits rotation of the C-arm about its axis. Often the support member is in the general shape of an L and is referred to as the L-arm, or yoke. Mobile C-arms have a third degree of freedom in that they are free to move horizontally along the floor and a fourth degree of freedom because the C-arm can be moved both upwardly and downwardly.
Obviously, a support structure that permits rotation and movement of such a C-arm must be constructed to withstand large torsional, tensile and compressive stresses. It is also desirable to provide a support structure heavy enough and a center of gravity low enough to avoid tipping when the C-arm is raised and rotated, which in some cases causes a dramatic shift in the center of mass of the equipment.
Additionally, C-arm x-ray equipment must be delicately positioned in order to render the image or images desired by the physician. Unfortunately, the weight of the support structure makes it difficult to position the C-arm. Therefore, it is desirable to design a source of frictional drag between the C-arm and the support member as well as on the C-arm track. It is also desired to provide an electric motor to move the C-arm both up and down due to the weight of the apparatus.
The delicate nature of the x-ray equipment requires delicate handling. Additionally, patients needing x-rays often require careful handling. In order to make the C-arm x-ray safer for the patient and to reduce the likelihood of damage to the C-arm itself, the device of the present invention provides for an anti-collision alarm and mechanism that stops movement of the C-arm upon contact with an object and then reverses movement of the C-arm to release the force exerted on the object by the machine.
It is therefore an object of the present invention to provide a method and an apparatus for use with a C-arm x-ray machine that emits a warning when the C-arm has run into an object, such as a patient, a gurney, or other obstacle. It is yet another object of the present invention to provide for such a method and apparatus that stops the C-arm when a part of it runs into an obstacle such that no damage occurs to the obstacle or to the C-arm, and prevents injury to the patient. A further object of the present invention is to provide such a method and apparatus that includes a programmable device in which the threshold of force required to stop the C-arm and sound the alarm may be varied. It is yet another object of the present invention to provide such a method and apparatus that requires relatively few parts, that can be easily manufactured and that can be readily installed on new or existing equipment.
The device of the present invention has obtained these objects. It provides for a load cell that is mounted at the bottom of the vertical column of the C-arm x-ray machine. This load cell converts the load, or the dynamic change in the load, on the vertical column into an electrical signal. The electronic signal is directed to an electronic circuit that filters and buffers the signal. The filtered signal is directed to a microcontroller. The microcontroller compares the load value with a database of preset load values and can operate to turn off the electric motor that raises and lowers the C-arm if the difference between the force on the load cell and the force expected by the microcontroller is greater than a certain amount. The microcontroller is adjustable such that the amount of force required to stop the motor can be varied. The electronic circuit in the method and apparatus of the present invention then reverses the electric motor to release the force exerted by the machine. Additional objects and advantages of the invention will be set forth in the description that follows. Other objects and advantages may be learned by practice of the invention.